Aromatic diamine compounds have been applied as a charge transport material of an electrophotographic photoconductor or as an organic electroluminescent (EL) device material. Particularly in the case where an aromatic diamine compound is applied as an organic EL device material, when the device material does not have a high glass transition temperature, the resultant organic EL device fails to exhibit heat resistance. Therefore, many attempts have been made to develop an aromatic diamine derivative containing in the molecule thereof a large number of aromatic rings (e.g., benzene rings or heterocyclic rings).
However, in general, an aromatic diamine derivative containing in the molecule thereof a large number of aromatic rings exhibits very poor solubility in a solvent. Such low solubility raises problems, including precipitation of diamine molecules in a solvent during the course of reaction, and limited reaction yield. For example, the following reaction:
is difficult to progress, because of the presence of a large number of intramolecular aromatic rings, which cause the raw materials and reaction intermediates to exhibit low solubility.
An aromatic diamine derivative is known to be produced through a reaction pathway applying a raw material such as α-naphthylamine, β-naphthylamine, 4-aminodiphenyl, or benzidine, which compounds are known to exhibit mutagenicity. Production of these compounds, which are designated “specified chemical substances,” is prohibited in Japan, and therefore demand has arisen for a production method which does not apply such a compound as a raw material or an intermediate.
For example, International Application PCT/JP02/02132 describes, as an example of such a production method, a method for producing an aromatic amine by reacting an aromatic amine having an arylalkyl group (e.g., a benzyl group) with an aromatic halide, without using a raw material or intermediate which may exhibit mutagenicity as described above.
However, difficulty is encountered in determining conditions for the aforementioned reaction, since the reaction requires a reduction reaction (e.g., hydrogenation) upon elimination of an arylalkyl group, which often causes reduction of an aromatic ring (i.e., a side reaction).